The present invention relates to a hydraulic drive system for driving an apparatus, with a drive unit which can drive the apparatus via a primary hydraulic circuit comprising a first and a second hydraulic displacement machine, and with a third hydraulic displacement machine, which is connectable or connected with the apparatus for transmitting mechanical energy, and a high-pressure accumulator which is hydraulically connected or connectable with the third displacement machine. In particular, the present invention relates to a hydraulic drive system which is used in a crane, in particular for driving a winch. Furthermore, the present invention relates to a hydraulic drive system which is used in a mobile equipment, in particular a reachstacker or a wheel loader, in particular as a traveling drive.
Such hydraulic drive systems usually include a primary drive unit, e.g. an internal combustion engine or an electric motor which drives one or more hydraulic pumps, in order to provide hydraulic energy for driving the apparatus. To increase the performance of such systems, it is first of all possible to dimension the drive unit larger, so as to be able to also provide more hydraulic energy. With increasing size of the primary drive unit, however, the costs, the packaging space and the energy consumption of the system are also increasing.
For this reason, hydraulic energy accumulators are used to an increasing extent, which are charged e.g. in braking phases, and in acceleration phases supply the hydraulic energy stored in the same to the drive system. Thus, the drive unit itself can be dimensioned smaller, as it is supported by the high-pressure accumulator during load peaks. In known hydraulic drive systems with such high-pressure accumulator, no satisfactory efficiencies can be achieved for the storage and release of energy. In addition, activation often is complicated.